ABSTRACT
The soil toposequence or ‘catena’ is a familiar concept in pedology which recognises the interrelationship between soils developed in different positions on a slope. The physical property which leads to the occurrence of lateral subsurface drainage in the soil is decreasing permeability with depth. D. Zaslavsky and A.S. Rogowski held such vertical anisotropy to be among the most important of soil properties. The depth of soil within the depression was generally observed to be inversely related to the steepness of the drainage line's ‘side slopes', the deepest soils being bounded by the shallowest sides. This relationship suggests that soil depth within the drainage line was controlled by a sequence of pipe growth, collapse and infill by erosion of the pipe's sides, aided by more rapid solutional weathering of the bedrock in the wetter floor of the drainage line.
